Study On Electric-field-driven Jet Deposition Micro-nano 3D Printing Based On A Single-plate Electrode

Micro/nano 3D printing is the current frontier direction and research hotspot of additive manufacturing,and it has a very wide range of applications in many fields such as biological tissue engineering,flexible electronics,new energy,and new materials.However,the existing micro-nano additive manufacturing technology faces many challenging problems in realizing low-cost,multi-material,macro/micro cross-scale 3D printing.In this paper,an electric-field-driven jet deposition micro-nano 3D printing based on a single-plate electrode(SP-EFD)has been proposed to provide a new solution with low-cost and high universality for micro-/nano-scale additive manufacturing and macro/micro cross scale 3D printing.Systematic researches,which involved theoretical analyses and numerical simulations and experimental explorations,have been carried out.The main research work and innovation are as follows:(1)This paper presents an electric-field-driven jet deposition micro-nano 3D printing based on a single-plate electrode technique which is based on electrostatic induction and electrohydrodynamic cone-jetting behavior.Differing from the traditional EHD printing with two counter electrodes and our previous proposed electric-field-driven jet deposition3 D printing with single nozzle electrode,this proposed technology is based on a selfinduced electrostatic field to achieve the 3D printing.In this method,the nozzle is no longer used as electrode,only a single-plate electrode is needed to connect to the positive electrode of high voltage power supply while the negative electrode is directly grounded,which not only overcomes the mandatory requirement of nozzle conductivity in traditional EHD jet printing,but also solves the discharge and breakdown problem of printing conductive materials on the conductive substrate.The micro-/nano-scale additive manufacturing by this proposed method can be achieved by combining the necking effect of Taylor cone formed by the self-induced electrostatic field between the printing material on the nozzle tip and the top surface of substrate,and multi-layer precise stacking by the polarization charges attraction between the printing material and the already printed materials on the substrate.Besides,considering the high-resolution and high-efficiency printing of various materials with different viscosities,two working modes,including the pulsed cone-jet mode and the continuous cone-jet mode,were proposed.(2)We establishes a mathematical model for SP-EFD jet deposition 3D printing and uses the finite element simulation software(COMSOL Multiphysics)to simulate the electric field distribution and intensity around the nozzle.In order to prove the advantages and features of this proposed method,a series of numerical simulation works have been carried out systematically: 1)the electric field distribution,strength and maximum field strength of three typical plate electrode materials(copper,aluminum and steel)are related to the conductivity of plate electrode;2)the electric field distribution and strength of three typical substrates(conductive copper plate,semiconductor silicon wafer,and insulating glass plate);3)the electric field distribution,intensity of two different material printing nozzles(conductive stainless steel nozzle,insulating glass nozzle)and the relationship between the maximum electric field intensity and the conductivity of the nozzle;4)the relationship between the deposition height of the printing material and the maximum field strength change.The simulation results show that: 1)SP-EFD jet deposition 3D printing technology can produce stable self-excitation electrostatic field between different plate electrodes and different printing nozzles and it can be concluded that the higher the conductivity of the single-plate electrode and the lower the conductivity of the nozzle,the greater the electric field intensity;2)SP-EFD jet deposition 3D printing technology needs to compensate the printing voltage as the printing height changes during the manufacturing of three-dimensional entities,which provides support for the subsequent experimental research on the three-dimensional structure.The printing mechanism is revealed through theoretical analysis and numerical simulation,as well as the feasibility and effectiveness of the proposed SP-EFD printing technology.(3)The process parameters have been optimized and the feasibility of printing with the nozzle(conductive steel nozzle and non-conductive glass nozzle),substrate(conductive copper plate,semiconductor silicon wafer,and insulating glass plate),and printing material(conductive silver paste and non-conductive polymer)has been verified by systematic experiments.The most important is that this method solves the discharge and breakdown problem of printing conductive materials on the conductive substrate.(4)Optimized process parameters combined with SP-EFD printing technology,four typical cases: Femtoliter volume drop and variable width lines,micro "wall" structure of polylactic acid(PLA),high-performance transparent electrode made of high viscosity silver paste,and multi-layer 3D scaffold have been printed successfully.